Abstract
Purpose :
Our group has previously shown that mesenchymal stem cells (MSCs) inhibit activation of innate immune cells, including neutrophils and macrophages. Here, we investigated the role and mechanisms by which MSCs regulate T cell function.
Methods :
MSCs derived from human bone marrow (hMSCs) were phenotypically characterized for their expression of CD45- CD34- CD73+ CD90+. To co-culture MSCs with T cells, CD4+CD25- T cells (purity >95%) were magnetically sorted from human peripheral blood mononuclear cells. Expression and secretion of IL-11 by MSCs were assessed by qRT-PCR and ELISA, respectively. Presence of IL-11 receptor was evaluated in activated CD4+ CD25- T cells by flow cytometry. Prior to co-culture, CD4+CD25-T cells were stained with CFSE, and their proliferation was measured by flow cytometry using CFSE dilution. We co-cultured CD4+CD25- T cells (stimulated with anti-CD3/CD28 beads at a 1:1 ratio) with MSCs at 1:1 ratio in the presence or absence of hIL-11 neutralizing antibody (20 µg/mL) for 24 hours (to initiate early activation) and 66 hours (to initiate proliferation). Early T- cell activation was assessed by evaluating the expression of CD40L and CD69 markers by flow cytometry
Results :
High levels of IL-11 were constitutively expressed by hMSCs at both mRNA and protein levels. IL-11 receptor was expressed by naive CD4+CD25- T cells, which increased by two folds upon CD3/CD28 stimulation. hMSCs significantly suppressed the activation of naïve T cells as evidenced by a reduction of approximately 70% in the expression of both CD69 (p=0.025) and CD40L (p=0.011). Following the neutralization of IL-11, MSC-mediated decrease in early T-cell activation was not observed. Additionally, CFSE dilution assay showed that hMSCs significantly suppress CD4+ CD25- T cell proliferation (p=0.006). However, this MSC-mediated suppression of T cell proliferation was reversed after neutralizing IL-11
Conclusions :
MSCs constitutively secrete high levels of IL-11, through which they suppress the activation and proliferation of CD4+ T cells
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.